1. Field of the Invention
This invention relates to improvements to a structure in which a pipe having a relatively small diameter and a thin thickness is fixed by welding to a flange coupling. More particularly, the pipe has a diameter less than about 20 mm and a thickness less than about 1.5 mm and made of carbon steel or stainless steel and used as a passageway for feeding oil and/or gas to vehicles, other various machines, installations, devices, etc. The flange coupling is provided on the side of the vehicles, or other various machines, etc.
2. Description of the Prior Art
In a conventional structure of this type, as illustrated in FIG. 4, a pipe P' is inserted at its cut end into a hole 12 in a flange 11 of an object and welded at 14 by gas or arc along the edge of the hole.
However, this method creates a thinned portion 15 on the pipe P', as shown in FIG. 5, due to a great difference in thickness between the pipe and the flange and due to local gas or arc welding in heating to thereby reduce the mechanical strength. This results in pipes having unequal bent forms. Irrational connection of a pipe having such a thinned portion under inconvenient and hard conditions would create cracks and breakage in the thinned portion and leakage of oil and/or gas due to possible vibrations applied to such pipe.